Heterogeneous silicotungstic acid constructed <i>via</i> defect and morphology engineering for boosting the oxidative desulfurization of fuel oil

It is well-known that defect engineering and morphology engineering are key strategies for giving an impetus to the catalytic activity of catalysts. This study reports the successful regulation of oxygen vacancy (O_V) defects and the morphology of a Keggin-type silicotungstic acid (SiW₁₂)-loaded N-doped carbon (NC) matrix, which is obtained by calcining a copolymer of acryloyloxyethyl trimethyl ammonium chloride (DAC) and acrylamide (AM) as precursors in air. It was unveiled that adjusting the proportion of AM in the copolymer could be simultaneously conducive to the targeted regulation of O_V defects of catalysts and their morphological evolution from bowls to spheres. The as-prepared O_V-SiW₁₂/SNC sphere catalyst showed an excellent oxidative desulfurization (ODS) performance with H₂O₂ as a green oxidant. Complete removal of DBT (2000 ppm) was achieved within 12 minutes at 60 °C with a large rate constant of 0.4055 min^-1. The outstanding ODS performance was critically ascribed to the highly active W sites promoted by the abundant O_V defects, and the easy diffusion and contact between the substrate and W sites were led by the spherical structure. Moreover, the as-prepared catalyst exhibited prominent reusability. This ODS reaction was found to follow a HO˙ radical mechanism.